- Synthesis of the 5-demethyl-6-deoxy analogue of sporogen AO-1, a sporogenic substance of Aspergillus oryzae
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Sporogen AO-1 is a sporulation-stimulating substance isolated from Aspergillus oryzae. We speculated that ring B would be important for the activity and designed a compound without functional groups in ring A. We synthesized the compound from 2-methylcycl
- Tamogami, Shigeru,Katayama, Masato,Marumo, Shingo,Isobe, Minoru
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- Hydrodealkenylative C(sp3)–C(sp2) bond fragmentation
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Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity—particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp3)–C(sp2) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.
- Smaligo, Andrew J.,Swain, Manisha,Quintana, Jason C.,Tan, Mikayla F.,Kim, Danielle A.,Kwon, Ohyun
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p. 681 - 685
(2019/06/11)
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- Enantioselective decarboxylative alkylation reactions: Catalyst development, substrate scope, and mechanistic studies
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α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center. Sly as a PHOX: The development of an enantioselective decarboxylative palladium-catalyzed allylic alkylation reaction, utilizing phosphinooxazoline ligands, is described. The catalyst is applied to a range of allyl enol carbonate, silyl enol ether, and allyl β-ketoester substrates to provide alkylated ketone products in excellent yield and good ee (see scheme). The utility of these products is demonstrated by their use in several asymmetric syntheses. Mechanistic studies are reported suggesting an unusual inner-sphere mechanism. Copyright
- Behenna, Douglas C.,Mohr, Justin T.,Sherden, Nathaniel H.,Marinescu, Smaranda C.,Harned, Andrew M.,Tani, Kousuke,Seto, Masaki,Ma, Sandy,Novak, Zoltan,Krout, Michael R.,McFadden, Ryan M.,Roizen, Jennifer L.,Enquist Jr., John A.,White, David E.,Levine, Samantha R.,Petrova, Krastina V.,Iwashita, Akihiko,Virgil, Scott C.,Stoltz, Brian M.
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supporting information; experimental part
p. 14199 - 14223
(2012/02/01)
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- The enantioselective Tsuji allylation
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The first catalytic enantioselective examples of the Tsuji allylation using enol carbonates and enol silanes are described. The products possess a quaternary stereogenic center and are useful building blocks for synthetic chemistry. Copyright
- Behenna, Douglas C.,Stoltz, Brian M.
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p. 15044 - 15045
(2007/10/03)
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- Resolution of Allylic Alcohols by Cholesterol Oxidase Isolated from Rhodococcus erythropolis
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The oxidation of non-steroidal compounds by cholesterol oxidase isolated from Rhodococcus erythropolis is reported for the first time.It was regio-, stereo- and enantio-selective.The enzyme oxidized preferentially the 2-cyclohexenyl-1-alcohols whose configuration is (S) at the reaction center.
- Dieth, Serge,Tritsch, Denis,Biellmann, Jean-Francois
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p. 2243 - 2246
(2007/10/02)
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- Chiral 2,2-Disubstituted Cyclohexanones; Annulation via Claisen Rearrangement Products
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The methyl enol ether of 2-methylcyclohexanone reacts regiospecifically with the optical active forms of but-3-yn-2-ol and but-3-en-2-ol. (R)-But-3-yn-2-ol yields an approximately 4:1 mixture of (R)-2-methyl-2-(R-buta-1,2-dienyl)cyclohexanone and the corresponding SR compound.By contrast the but-3-en-2-ol reaction is ca. 96percent enantioselective; (R)-but-3-en-2-ol gives (R)-2-(trans-but-2-enyl)-2-methylcyclohexanone and (S)-but-3-en-2-ol gives the corresponding (S)-cyclohexanone.These Claisen rearrangement products have been transformed into Robinson-type annulated ketones.Cleavage of some highly hindered esters has been carried out efficiently by sodium methylsulphinyl-methanide in dimethyl sulphoxide.
- Grattan, T. J.,Whitehurst, J. S.
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- THE CONVERSION OF (-)- AND (+)-DIHYDROCARVONE INTO CHIRAL INTERMEDIATES FOR THE SYNTHESIS OF (-)-POLYGODIAL, (-)-WARBURGANAL AND (-)-MUZIGADIAL
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(-)-Dihydrocarvone was converted into (-)-(4aR,8aR)-3,4,4a,5,6,7,8,8a-octahydro-4a,8,8,trimethylnaphthalene-2(H)-one (1) via an efficient route in which a Wolff-Kishner reduction, accompanied with a double bond isomerisation brought on a major simplification.Ketone 1 is a suitable intermediate for the syntheses of the insectantifeedants (-)-polygodial and (-)-warburganal. (+)-Dihydrocarvone was converted into (+)-(4aR,7S,8aR)-4a,7-dimethyl-8-methylene-3,4,4a,5,6,7,8,8a-octahydronaphthalene-2(1H)-one (2), an intermediate ketone for synthesis of (-)-muzigadial.
- Jansen, Ben. J. M.,Kreuger, Jacoba A.,Groot, Aede De
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p. 1447 - 1452
(2007/10/02)
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- Chiral 2,2-Disubstituted Cyclohexanones; Annulation via Claisen Rearrangement Products
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The methyl enol ether of 2-methylcyclohexanone reacts regiospecifically and enantioselectively with (R)- and (S)-but-3-en-2-ol to give respectively, the (R)- and (S)- forms of 2-methyl-2-(trans-but-2-enyl)cyclohexanone.
- Grattan, T. J.,Whitehurst, J. S.
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- OPTICAL RESOLUTION OF KEY COMPOUNDS OF PROSTAGLANDIN SYNTHESIS AND RELATED COMPOUNDS
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Hundred per cent optically pure bicyclic lactones and bicyclic ketones were easily obtained by complexation method with optically active 1,6-bis(2-chlorophenyl)-1,6-diphenylhexa-2,4-diyne-1,6-diol.
- Toda, Fumio,Tanaka, Koichi
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p. 885 - 888
(2007/10/02)
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- N,S-DIMETHYL-S-PHENYLSULFOXIMINE. A REAGENT FOR THE OPTICAL RESOLUTION OF KETONES
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The addition of the α-lithio derivative of (+)- or (-)-N,S-dimethyl-S-phenylsulfoximine to selected dl-ketones was carried out at -78 deg C in tetrahydrofuran followed by acid quench at that temperature to produce mixtures of diastereomeric β-hydroxysulfoximines.The optically-active diastereomers were chromatographically separated on silica gel.The purified diastereomers were thermolyzed at ca. 130 deg to produce optically-active ketones and the optically-active sulfoximine which could be recycled.
- Johnson, Carl R.,Zeller, James R.
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p. 1225 - 1234
(2007/10/02)
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